A number of potentially important new synthetic routes to heterocyclic compounds, including furans, butenolides, benzofurans, chromenes, coumarins, isocoumarins, Beta-lactams, tetramic acids, pyrroles, indoles, quinolines, isoquinolines and benzodiazepines, are outlined. These heterocycles occur widely in nature and exhibit substantial physiological activity. They have found use in the treatment of cancer, circulatory and heart ailments, and bacterial and fungal infections. A broad spectrum of antibiotic activity is evident among these compounds. Our previous work on new synthetic applications of organometallic compounds has suggested a number of novel new approaches to these ring systems, all of which take advantage of the ease with which organopalladium compounds can be prepared from either organomercury or -thallium compounds or via direct palladation of acetylenes and aromatic compounds, and the facility with which organopalladium compounds react with carbon monoxide or olefins to generate new carbon-carbon bonds. The appropriate positioning of functional groups should allow novel new syntheses of the heterocyclic ring systems mentioned above. Successful completion of this work shold (1) open up entirely new routes to these naturally occurring, biologically active heterocycles, (2) provide a number of interesting new compounds which might be expected to show physiological activity and hopefully medicinal utility, and finally (3) simplify many a synthesis of these vitally important heterocycles.